06/10/2020

Compare : Three Phase Induction Motor & Transformer

Construction

  • The stator and rotor magnetic field rotate at synchronous speed with each other in the case of three phase induction motor. 
  • These fields are stationary with each other therefore a three phase induction motor is equivalent to transformer with air gap between stator and rotor winding. 
  • The three phase induction motor is considered as transformer with short circuit secondary ( rotor ).

Magnetizing current

  • The magnetizing current and magnetic leakage flux for an induction motor is higher than that of transformer for same rating because of air gap between stator and rotor.

Efficiency

  • The efficiency of transformer is much higher as compared to induction motor because there are no mechanical losses in the transformer. 
  • The efficiency of power transformer closes to 99.8% whereas it is 80 to 88% in the case of three phase induction motor.

No load current

  • The no load current of the transformer is hardly 2 to 5% to that of full load current whereas it is 25 to 40% of full load current in the case of induction motor. 
  • This is due to fact that the flux passes through silicon steel in the transformer which has low reluctance whereas in the case of induction motor, the flux passes through stator to rotor via air gap which has high reluctance.

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